Crusted deep-fried foods are deep-fried food products obtained by coating the surface of an ingredient with a crust material and deep-frying the coated ingredient by heating the same in oil. By deep-frying both the ingredient and the crust simultaneously in a balanced manner, the taste/flavor of the ingredient is condensed as a result of the ingredient being heated in a state where it is covered in a crust, whereas the crust is provided with a roasted-oil flavor and crispy texture as a result of moisture being evaporated by the high-temperature oil during deep-frying, and a synergy therebetween provides the deep-fried food with its characteristic flavor and texture. However, in order to obtain a deep-fried food having such characteristic flavor and texture, a person cooking the food needs to have reasonable experience in terms of e.g. temperature management of oil used for deep-frying, how to prepare and size the ingredient, the amount of batter/crust material to be applied, the viscosity and degree of mixing of the batter, etc. In ordinary households, etc., it is rare that deep-frying is performed with such experience, and thus, often, the crust becomes too thick and stiff, or the crust has a texture lacking crispiness.
Further, at the time of producing a deep-fried food, usually, a batter (slurry for crust) is prepared by mixing a crust material, which includes wheat flour as a main component, with water, and an ingredient is coated with the batter. However, wheat flour conventionally used for a crust material has poor dispersibility to water. Further, in a solution state, gluten included in wheat flour becomes viscous by forming a mesh structure with the lapse of time. Thus, it is impermissible to keep stirring the batter for a long time to improve dispersibility etc., and the batter needs to be used promptly after preparation. To address the above, wheat flours more suitable for crust materials have been proposed.
For example, Patent Literature 1 discloses a wheat granulated product for tempura having good flavor and texture even when reheated after being cooked, the wheat granulated product including a wheat flour and 0.01 to 0.5 parts by mass of an emulsifier with respect to 100 parts by mass of the wheat flour, and having an average grain size of from 100 to 180 μm. In relation to a process for producing this wheat granulated product for tempura, paragraph [0012] of Patent Literature 1 describes that a solution prepared by adding water to a mixture including a wheat flour and an emulsifier is granulated while being dried under conditions where the hot-air temperature is from 120 to 140° C. and the drying time is within 5 seconds. Further, Patent Literature 2 discloses a crust composition for deep-fried foods that includes a heat-treated wheat flour, oxidized starch, and a sucrose fatty acid ester. Paragraph [0011] of Patent Literature 2 describes that the heat-treated wheat flour is produced by heating wheat flour at a temperature from 80 to 120° C. for 20 to 90 minutes.
Patent Literature 3 discloses a heat-treated wheat flour for deep-fried foods wherein the starch included therein is substantially not pregelatinized, the gluten vitality is from 90 to 98% of untreated wheat flour, and the gluten swelling degree is from 105 to 155%. The heat-treated wheat flour for deep-fried foods disclosed in Patent Literature 3 does not include an emulsifier, and is produced by introducing wheat flour into a hermetically-sealed high-speed stirring machine which is in a pressurized state with saturated water vapor introduced therein, and subjecting the wheat flour to a heat-moisture treatment under conditions where the product temperature is from 65 to 80° C. and the residence time is from 2 to 20 seconds. Further, Patent Literature 4 discloses a wheat flour composition suitable for steamed food products, such as steamed buns or steamed bread, obtained by mixing a wheat flour and 0.1 to 2.0 parts by mass of an emulsifier with respect to 100 parts by mass of the wheat flour, and then subjecting the mixture to an indirect heating treatment under conditions where the product temperature is from 80 to 150° C. and the heating time is from 5 to 120 minutes. In the indirect heating treatment, heated water vapor is used as a heat source, and the heated water vapor is not directly applied to the mixture including the wheat flour and the emulsifier, but is applied to a container containing the mixture, and the mixture inside the container is heated indirectly.
The techniques disclosed in Patent Literatures 1 to 3 can provide deep-fried foods with favorable texture, but an even crispier texture is demanded of crusts of deep-fried foods. There is also a demand for a crust material, which is a raw material of a crust, having excellent dispersibility in water and excellent workability such as batter preparability, and capable of simplifying the labor of producing deep-fried foods.